Hypodermic injector



Dec-17, 1957 A. vENDlTTY ET AL 2,816,543

HYPODERMIC INJECTOR 2 Sheets-Sheet 1 AH/log qnd Jo/m Sez/gerer rloeNEVsY HYPODERMIC INJECTOR Anthony Venditty, Detroit, and John 0. Scherer,Grosse Pointe, Mich., assignors to R. P. Scherer Corporation, Detroit,Mich., a corporation of Michigan Application July 12, 1954, Serial No.442,613

7 Claims. (Cl. 12S-173) This invention relates to av needlelesshypodermic injector capable of injecting a fine stream or jet of liquid.

medicament at high velocity through the epidermis. More particularly,the invention constitutes an improvement over the injector described inthe copending application of Robert P. Scherer, Serial No. 94,579, ledSeptember 28, 1953, now Patent No. 2,704,543. The instrument describedin that application is adapted to discharge liquid medicament from anampule at two diierent pressure stages, an initial high pressure stagefor causing the jet stream to distend 'the skin and penetrate to apredetermined depth, followed by a reduced pressure stage'for completingtransfer of the liquid from the ampule through the opening producedduring the high pressure stage. The two pressure stages are producedbyaspring-actuated dual plunger assembly comprising a primary plunger orsmall diameter slidably mounted within' a secondary plunger having adiameter equal to that of theilexible rubber-like follower or stopperwithinthebore of the ampule. The follower is cup-shaped and is adaptedto expel liquid through a minute orifice in thev end of the ampule as itadvances down the bore. `As thepower spring expands, the primary plungerexerts a force against the central portion of the bottom of the followerto distend that portion a short distance and simultaneously eject asmall amount of liquid from the oriice in the ampule under highpressure. The volume of liquidejectedduring the tirst or high-pressurestage determines the depth of penetration of the stream below thesurface. After the primary plunger has traveled to the end of itsstroke, which is relatively short, the secondary plunger engages theentire area of the bottom of the follower and moves the follower downthe bore of the ampule to complete the injection at reduced pressure.The reduction in pressure, of course, is due to an increase in thearea-engaged by the plunger. The pressure during the second stage isjust enough to feed the liquid through the channel made during the irstpressure stage. Y Y

Since the primary plunger only distends the follower and does not moveit, the follower does not travel down the bore of the ampule untilengaged by the secondary plunger. Therefore, part of the energy suppliedtothe plunger to generate pressure is momentarily diverted in overcomingstarting friction in advancing the follower. The result is that thepressure of the liquidV jet does not drop directly from lirst stage tosecond stage and then level oil, but dips below the normal second stagepressure at the point where the starting friction must beovercome, andthereafter increases to the normal second stage pressure. This reductionin pressure and `subsequent sudden increase in pressure due toovercoming `the friction of the follower in the ampule is highlyundesirable because in some patients'the resultingfswurgeY causes pain.It is one ofthe objects lof the present iiiveritionto provide aninstrument for Vtwo-stage pressure injection in which the pressure isreduced to th'e second Vstage 'without l theunde'sirable momentary drop'just vdescribed.V` i

vAnother object is'to provide 'two pressure stages through nited StatesPatent O 2,816,543 Patented Dec. 17, 1957 a single plunger. These andother objects will become apparent from the following description andthe accompanying drawing, in which:

Figure 1 is a longitudinal sectional view through an instrumentillustrating the invention;

Figure 2 is an enlarged longitudinal sectional view of the lower portionof the instrument of Figure l showing the position of the parts of theplunger assembly at the beginning of the low pressure portion of theplunger stroke;

Figure 3 is a transverse section along the line 3-3 of Figure 1;

Figure 4 is a longitudinal sectional view of the lower portion of theinstrument shown in Figure 1 illustrating a modification of the plungerassembly;

Figure 5 is a similar enlarged view of the lower portion of theinstrument shown in Figure 1 illustrating another modification of theplunger assembly; and

Figure 6 is a transverse section along the line 6 6 of Figure 5.

Broadly, this invention consists in the provision of a single plungeradvanced by forces of two different magnitudes to produce the twopressure stages desired. Since pressure equals force divided by area, itis apparent that pressure may be increased either by increasing theforce or decreasing the area. In the construction of the presentinvention the force ou the ampule follower may be varied to produce thechange in pressure. The change in force is accomplished by mechanicallymultiplying the force applied to the plunger during the first part ofthe stroke and then transmitting the force of the same magnitudedirectly to the plunger, without the aid of the multiplier, for theremainder of the stroke. By this means the pressure resulting from themultiplied force is high, whereas that resulting from directtransmission is relatively low. The ratio of the pressures may becontrolled by changing the proportions of the force-multiplying device.

For a detailed description of the invention, reference is now made tothe drawing in which the numeral 10 designates a body housing most ofthe mechanism of the injector. A dosage sleeve 12 is screwed onto thethreaded lower or ampule-containing end of the injector, and a windingsleeve 14 is rotatable on the upper end thereof. The sleeve 14 has aninturned flange 16 coacting with an annular ridge or ring 18 on the body10 to prevent longitudinal movement in one direction relative to thebody. A latch housing 20 is screwed into the rear or upper end of thewinding sleeve 14 with a thrust bearing assembly 22 interposed betweenthe body and the latch housing.

A release button cap 24 is threaded on the latch housing 20 and theentire assembly of the winding sleeve 14, latch housing 20 and cap 24 isheld in assembled relation by a set screw 26 engaging all three partsand sealed in place, as best shown in Figure 3.

The dosage sleeve 12 has threaded on its lower end an ampule holder 30adapted to -receive an ampule 31 having medicament 32 therein and aflexible cup-like follower 33, preferably made from an oil-resistantrubber, such as polychloroprene, Buna N, or the like. The ampule isprovidedV with a reduced discharge nozzle 34 perforated by a minutedischarge orice 35. The ampule holder is covered by a resilient nose36which may also be made from polychloroprene rubber or the like.

The internal mechanism of the injector construction shown in Figure 1includes the novel plunger assembly of the Ainvention, which multipliesvthe force transmitted to the plunger 40,* which is adapted to advancethe ampule follower 33 within/the ampule 31. The assembly consists of aplunger 40 having an integral head 41, the head recess 42 providedwithin the disc-like bearing member or cam carrier 43, and a piston-likecam actuator 52. Cam carrier 43 is adapted to slide axially within thedosage sleeve 12. To permit assembly of the plunger 40 with the camcarrier 43, three flange-like ears 44 extending outwardly .from the head41 and equally spaced about the circumference thereof serve to lock thehead 41 beneath the llange 45 which extends radially into the recess 42of the `cam carrier 43. Flange 45 has three circumferentially-spacedslots which cooperate with the ears 44 in the manner of a bayonetconnection to permit the head 41 to be inserted in the recess 42 whenthe ears and slots are aligned. The head 41 is then turned about 60 sothat the ears 44 are located beneath the ange l45 to prevent completeseparation of the plunger 40 .from the calm carrier 43. Obviously, thenumber of ears and corresponding slots is not critical and any suitablenumber may be employed.

To facilitate movement of the plunger 40 with respect to the camlcarrier 43, a cam actuator 52 is adapted to slide axially within ablind central opening 55 provided in the plunger. Shaft A53 comprisingthe lower end of actuator 52 is of reduced diameter for this purpose. Tomove the plunger 40 under multiplied force, three cams 47 of triangularwedge-shaped cross section are slidably seated within radial guide slots48 cut in the top surface of the head 41 and equally spacedcircumferentially. The right side of theisection shown in Figure l istaken through slot 48. The number of cams and corresponding slots,

of course, may vary, but we have found 'three to be suitable for thepurpose. The sides of the triangular cams 47 are flat, with the edgesrounded where the sides meet each other. The cam carrier 43 has acentral opening t) and three radial slots 49 cut in the bottom of therecess 42. Slots 49 are aligned radially with slots 48 and cooperatetherewith to guide cams 47. The slots 49 slope centrally toward the topsurface 51 of the cam carrier 43 and join with the opening 50. The slopeof each slot 49 is equal to the angle 59 between the top and bottomsides of the cams 47 so that the bottom .sides of each cam will lie flatagainst the bottom of the corresponding slot 48 in the head 41 while thetop sides of each cam lie Hat against the .sloping surface 49 in the camcarrier 43. When the head 41 is in the position shown in Figure l withits top surface in contact with the bottom of the recess 42, the shortsides or ends of the cams 47 project into the opening 50 a slightdistance. These ends are adapted to lie against corresponding wedgeslots 54 provided therefore in the vcam actuator 52. The flat ends ofcams '47 lie .insubstantially complete contact with the wedge slots 54,as .shown in .Figure 1. As indicated, the cam actuator has a lower end53 o'f reduced diameter which slides within the blind .axial bore 55 ofthe plunger 40. A -coil spring 58 is .provided in the bottom of the bore55 to return the cam actuator 52 to its original position when theinjector is reset. The upper end of the actuator slides within theopening 50 provided therefor in the cam carrier. When 'the actuator 52moves downwardly, the wedges or cams 47 are forced outwardly by thewedge slots S4, to Aforce the piston downwardly'.

By changing the angle 59 which makes the wedge steeper or shallower, theratio of the force applied by the cam actuator 52 to the force appliedby the plunger 40 may be varied. The smaller the angle, the larger themechanical advantage or force transmitted to plunger 40.

Force applied to the end of the cam actuator -52 by the screw 62, asexplained herenbelow, serves to 'slide cams 47 radially within guideslots 48 and 49 as'the wedge slots 54 of the cam actuator bring'pressure 'to bear against the cams 47, thus causing the head 41 to moveaway from the cam carrier 43.

The flanged Vend 37 of the plunger 40 slides within the bore of theampule 31 to engage the follower '33 for ejecting liquid from theampule. A rubber washer 38 is provided in the bottom rof the cavity ofthe sleeve 12 to pro- 4 vide a resilient cushion for the plungerassembly when it is operated without an ampule in place. When dischargedwith an ampule in place the plunger will not descend this far.

The mechanism for propelling the assembly comprises a nut 60, a screw 62and a plurality of power springs 64 disposed around the screw 62 withinthe body 10. The nut is sleeve-like in character and has a clover leafshaped head 66 provided with spring seats for the springs 64, whichsprings at their opposite ends seat against a partition 68 of the body10. The nut 60 has threads 61 at its upper end which cooperate with thethreads of the screw 62. The nut 60 will not rotate with respect to thebody 10, but is adapted to move longitudinally therein. The upper end ofthe screw as shown in Figure 1 is provided with a head 70 providing alatching shoulder 71. The screw head 70 terminates in a bifurcatedportion which results in a pair of spaced blades 72, the head with 'its,blades being slidable in a square opening 21 in the latch housing 20.As shown in Figure 3, the latch housing is provided with a cross slot 23in which the latch 25 is lpivotally mounted. For this purpose a pivotpin 27 is press-tted in the latch and has its ends rotatable in thelatch housing. The latch 25 substantially spans the width of the slot 23and the space between the blades 72 of the screw and is of the shapeshown in Figure 1, having a latching shoulder and a spring socket 76. Alatching spring 77 has one end seated in the socket and its other endseated in an opposing socket 78 in the latch housing for tending to:rotate the latch counterclockwise.

Slildably mounted in the release button cap 24 is a release button 80having a cross bar 82 attached thereto and slidable in the slot 23 ofthe latch housing 20 and the space between the blades 72 of the screw 62back of the latch 25. When the button 80 is depressed, the latch v25 isrocked against the bias of the spring 77. A latch roll 83, rotatablymounted in the latch housing, prevents the screw 62 which is biasedupwardly from moving until the latch 25 is released, thus permitting thelatch roll 83 .to'rotate out from under the shoulder 71.

In operation, the winding sleeve 14 is rotated causing the 'screw -62(latched against axial movement) to turn and lift the nut 60 to compressthe springs 64 seated in 'the head '66. Then, the ampule 31 is placedwithin the holder 30 and secrewed onto the end of the injector. Theparts are then in the position shown in Figure 1, the ampule follower 33being yin contact with end 37 of plunger-40..

Release is accomplished by depressing the button 80. 'The latch 25 isrocked against bias of spring 77 which permits the latch roll 83 torotate out from under the shoulder 71. Upon releasing the latch, thesprings 64 immediately expand and screw 62 is carried downwardly bythenut 60. The lower end of the screw 62 is pointed and seats in a conicaldepression in the end of the cam actuator 52. As it moves downwardly thecam actuator forces lthe cams 47 outwardly within the radial guide slots48 and 49. Since the cam carrier 43 is supported by the posts r andcannot n'se within the instrument, the head 41 moves away from the camcarrier 43 as the cams move outwardly to cause the piston 40 to movedownwardly and transmit the force from the screw 62, multiplied throughthe cams 47, to the follower 33. The multiplied forces imparted to thepiston 40 causes liquid 32 to be `ejectedfrom the ampule at highpressure. The magnitude of the force exerted by the plunger 40 may beincreased or decreased 'as indicated previously by changing the angle 59lof the cams 47 to vary the mechanical advantage provided thereby.

The plunger 40 advances under this multiplied force a distancedetermined by the mechanical advantage provided by the Wedges. Forexample if the mechanical advantage is 3 to l this distance will beequal to l/a the distance travelled by the actuator 52. When `the wedgeshave been `fully extended into the slots 48 and 49 in which they slide,the liangev 66 of nut'60 engages thiesurfacesl -of the cam carrier 43,and the plunger 'assembly then moves as a unit to expel the remainingliquid 32 from the ampule 31 under reduced pressure. At the instant thenut makes contact with surface S1 the parts are in the relativepositions substantially as shown in Figure 2. Resetting is accomplishedas with the conventional 'insrtument The screw is turnedcounterclockwise to latch it and then in a clockwise direction tocompress the springs. The ampule is then replaced and the instrument isready for another injection.

A modification of the force-multiplying means shown in Figures 1 and 2is illustrated in Figure 4. The three triangular liat-sided cams orwedges 47 have been replaced with three balls or spheres 69 with matingslots 48a and 49a. Apart from this replacement, the construction of theplunger assemblies are exactly the same. The balls are large enough sothat they project into the central opening 50 in the cam carrier 43 andbear against the' wedge surfaces 54a of the cam actuator 52. The balls69 will roll and/ or slide up the slots 49a and 48a in the cam carrier43 and the plunger head 41, respectively, as the actuator 52 movesdownwardly. The operation of this unit is the same as that described inconnection with Figures l and 2.

A further modification of the invention is illustrated in Figures and 6.The force-multiplying means illustrated here employs a series ofpie-shaped levers in place of wedges or cams. The force is transmittedfrom the screw 62 to the plunger 100 through ve pie-shaped levers 104which in assembled relation comprise a disc. The plunger 100, shown inFigure 5, has an integral disc-like head 102 which slides axially withinthe dosage sleeve 12 of the instrument. The levers 104 which arepie-shaped in plan View, are arcuate in cross section, as shown inFigure 5. The levers are arranged so that the outer arcuate portions 105are contiguous and lit inside the circular dosage sleeve 12. The bottomarcuate surface 109 of each lever is adapted to bear on the at uppersurface 101 of the plunger head 102. The outer extremities 110 of eachlever 104 bear against the lower ends of body posts 90a, which serve asstops. The pointed inner extremities 108 of the levers 104 bear againstthe end of the screw 62a. As shown in Figures 5 and 6, when the innerextremities 108 are in raised position (plunger 100 being retracted),the sides 107 of the levers separate slightly, the separating distancedecreasing toward the circumference or peripheral arcuate edges 105. Thenumber of levers 104 is not critical, any convenient number beingsatisfactory.

vIn operation, the descending screw 62 strikes the inner extremities 108of the levers causing the levers to rock radially toward the center ofthe plunger head to push the plunger 100 downwardly with multipliedforce by reason of the mechanical advantage provided through the levers.Because the bottom bearing surface 109 of each lever is arcuate inshape, the fulcrum of the lever advances progressively radially inwardlyfrom the extremities 110, which are prevented from moving upwardly bythe posts 90a. When the inner extremities 108 of the levers aredepressed against the surface 101 to the point where the projection onflange 66 of the nut 60 engages the levers, the plunger and the leversadvance together as a unit. While the force from the screw 62 is appliedto the plunger 100 through the levers, the pressure at which the uid isexpelled from the ampule is relatively high. When the levers havecollapsed to the point where nut 60 makes contact with the top surfaceof levers 104, the force is then applied to the plunger without themechanical advantage and the pressure is consequently reduced.

From the foregoing description it will become clear that variousmodifications in the force-multiplying plunger assembly can be madewithout departing from the spirit of this invention. The invention isnot intended to be' 6 limited to the specific constructions illustratedother than as necessitated by the scope of the appended claims.

We claim as our invention:

1. In a hypodermic injector, an assembly comprising an elongated body,an ampule holder detachably connected to the end thereof and adapted tohold an oriced ampule, a single plunger slidably mounted within saidbody and adapted for engaging and propelling a follower within saidampule to discharge liquid contents through the orifice, said plungerhaving a head integral therewith and a blind axial bore, a disc-like camcarrier slidably mounted within said body and having a recess in `oneface thereof terminating in a central opening aligned with said axialbore, said head being reciprocatively mounted within said recess,force-multiplying cams interposed between the bottom of said recess andsaid head and adapted to move radially to force said head away from saidcam carrier, a cam actuator slidably mounted within said central openingand said bore of the plunger, and power means within said body adaptedto engage said cam actuator and said cam carrier sequentially to movesaid plunger through the action of said cams with multiplied force, andto advance the plunger and cam carrier as a unit with a force of normalmagnitude, said power means including means for storing energy thereinand means for suddenly releasing the energy thus stored.

2. The hypodermic injector of claim 1 in which the force-multiplyingcams are wedge shaped.

3. The hypodermic injector of claim 1 in which the force-multiplyingcams are spherical.

4. ln a hypodermic injector, an assembly comprising an elongated body,an ampule holder detachably connected to the end thereof and adapted tohold an oriced arnpule, a single plunger slidably mounted within saidbody and adapted for engaging and propelling a follower within saidampule to discharge liquid contents through the orifice, said plungerhaving a head integral therewith, force-multiplying levers of arcuatecross section supported by said head, the outer extremities of saidlevers bearing against stops to prevent movement away from said head,said arcuate levers being adapted to rock radially against said head,and power means within said body adapted to engage the inner extremitiesof said arcuate levers to move said plunger through the rocking actionof said levers with multiplied force, and then to engage the depressedlevers in an area outside said inner extremities to advance directly theplunger and the levers as a unit with a force of normal magnitude, saidpower means including means for storing energy therein and means forsuddenly releasing the energy thus stored.

5. In a hypodermic injector, an assembly comprising an elongated body,an ampule holder detachably connected to one end thereof and adapted tohold an oriced ampule, a single plunger slidably mounted within saidbody and adapted for engaging and propelling a follower within the boreof said ampule to discharge liquid con tents through the orifice, powermeans for propelling said plunger including means for storing thedriving energy therein, means for suddenly releasing the energy thusstored to perform propulsion of the plunger and follower, andforce-multiplying means between said power means and said plunger andadapted to increase the force applied to the plunger during the firstpart of its stroke.

6. In a hypodermic injector, an assembly comprising an elongated body, acylindrical chamber in one end thereof having a bore terminating in aminute orifice and adapted to hold liquid to be discharged from theinjector, a follower within the bore of said chamber, a single plungerslidably mounted within said body and adapted for engaging andpropelling a follower within the bore of said chamber to discharge theliquid through the orifice, power means for propelling said plungerincluding means for storing the driving energy therein,

means for suddenly releasing the energy thus stored vto performpropulsion of the plunger and follower, and force-multiplying meansbetween said power means and said plunger and adapted to increase ltheforce applied to the plunger during the rst part of its stroke.

7. In a hypodermic injector, an assembly comprising an elongated body,an ampule holder detachably connected to the end thereof and adapted tohold an oriced ampule, a single plunger slidably mounted within saidbody and adapted for engaging and propelling a follower l within saidampule to discharge liquid contents through the orifice, said plungerhaving a head integral therewith, a disc-like cam carrier slidablymounted within said body adjacent said head, force-multiplying camsinterposed hetweensad cam ycarrier and said head adapted 'to moveradiallyto lforce said head away from said cam carrier, a cam actuatorfor moving said cams and power means within said body adapted 'to engagesaid cam actuator and said cam earrier sequentially to move said plungerthrough the actionof said cams with multiplied force, and to advancefthe plunger and cam carrier as a unit with aforce o'f normal magnitude,said power means including means for storing energy therein and meansfor sud denly releasing the energy thus stored.

No references cited.

